If your valves are not fully opening there is a chance of running a lean mix. That will amplify w/ rpm's, and build heat exponentially. The heat will pre ignite the lean mix, and give you detonation. The higher octane/flash point of hi test fuel can control this (to a certain extent) Don't loose any sleep over it, but the valve adjustment is one of the most important things to do correctly. The correct breathing/temp. of your cylinder depends on it.
